"If they would have did their job right and actually made a police report or whatever, everything with Sandra could have been prevented and she could have been here today," said the 18-year-old sister, who requested her name not be used.

Police in Tracy, Calif., said they acted properly in the case of the 7-year-old, whose name is being withheld.

Sandra's body was found April 6, stuffed into a suitcase that had been thrown into an irrigation pond. Huckaby was charged days later with murder and the special circumstances of kidnapping, lewd and lavicious acts with a child and rape with a foreign object, which qualify her for the dealth penalty should prosecutors seek that option.

Like Sandra, the 7-year-old girl used to play with Huckaby's 5-year-old daughter, Madison. The young woman said her sister had gone to the park that day in January with Huckaby despite not getting permission to do so.

When the little girl couldn't be found, the family called police, the older sister told several news outlets, including ABC News, in a phone interview. Cops searched the entire mobile home park, "but she was nowhere to be found in here," she said. "Then a couple hours later after the detectives and everybody came, Melissa brought her home."

According to police logs she was returned in a purple Kia Sportage that matches the description of Huckaby's car that was towed by police after Sandra's murder.

The teen said her little sister, who was also a playmate of Sandra's, had been drugged before she came home.

"Her speech was slurred ... like she had a really bad lisp," the woman said. "And she would cry a lot like something was wrong with her. She couldn't stand up without help. She couldn't walk. Everytime she tried to walk, she would fall."

"So they took her to the hospital, and the hospital told us that she had muscle relaxants in her system," the 18-year-old said.

Police Say Full Investigation Done After January Incident

The police logs from that day show that the little girl had benzodiazepines in her bloodstream. The drugs are often prescribed as a sedative or to induce sleep, relieve anxiety and muscle spasms and prevent seizures.

The teenager said the family was worried that her sister may have been abused that day, but tests at the hospital showed no evidence of sexual molestation.

The alleged victim's older sister said she isn't sure the police even questioned Huckaby after the incident.

"The policemen, the detective, they told us not to say nothing to Melissa," she said. "I don't know. They said that they talked to Melissa, but I don't think they did. Because if they talked to Melissa, then something else would have been done."

The teenager also claims the family filed a police report, despite police insistence to the contrary.

Because all reports filed in connection with the brief disappearance of the 7-year-old are now part of the Cantu investigation that will be used to prosecture Huckaby, Sheneman said he could not share any details of what police had learned.

The young woman said her sister had been treated well previously when she had been with Huckaby, playing with her daughter. And she had never seen her act inappropriately with children before that day. But after her sister returned home on Jan. 17, the woman said she was never allowed to be with Huckaby again.

The girl's family said they were surprised to learn that Huckaby had been arrested in Sandra's murder because they, like many others, including the police, had expected the suspect to be a man. But still, she said, "there was some suspicion in my house after what happened to my sister."

The teenager said her family is confident police arrested the right person for Sandra's murder.

"It's sickening," she said. "How you can do that to somebody so young, and so innocent for no reason?"

Sandra'sprivate funeral was held last Wednesday. One day later the request was filed to exhume her body so the defense for accused killer Melissa Huckaby would have an opportunity to conduct its own autopsy.

Huckaby's attorney, Deputy Public Defender Samuel Behar, professed to have no knowledge of the case when contacted by ABCNews.com, but a court document filed by Behar Thursday indicated the request was based on the deputy district attorney's belief that Sandra had suffered "genital trauma consistent with forcible penetration."

In the court document, Behar said the defense needed to examine the alleged trauma so Huckaby would be able to defend herself. He also requested the exhumation take place quickly, alleging that deterioration would cause Sandra's body to have "progressively diminishing value."

A San Joaquin Superior Court spokeswoman said a hearing on the exhumation request is scheduled for Friday, the same day Huckaby is due back in court for a further arraignment where she would have the opportunity to enter a plea.

San Joaquin Deputy District Attorney Robert Himelblau told ABCNews.com Monday that his office would be filing a response to the request but did not elaborate.

Chavez said the family was mostly holding up as best they could. They were shocked at the massive turnout for Sandra's public memorial service, held Thursday.

"We were very surprised," Chavez said. "We knew she touched a lot of people."

Mourners and well-wishers stopped by the mobile home park for days after Sandra was found, leaving flowers, signs, candles and stuffed animals. But now that the focus has turned to Huckaby's trial, Sokoloski said, the park, once crawling with police and reporters, has started to quiet down.